The invention relates to a method and equipment-for implementing supplementary services to be taken into account in intelligent-network-based charging mechanisms.
An intelligent network (IN) is able to provide a subscriber of a telecommunications network, such as a wired network or a mobile telephone network, with a plurality of various services. Such services include a virtual private network (VPN) which allows the use of short numbers between subscribers belonging to a local network, and a personal number in which the intelligent network reroutes the calls directed to a personal number in a manner controlled by the subscriber. An example of such an intelligent network is described in recommendations of the ITU-T Q-1200 series, of which Q-1210 to Q-1219 define a set of features known as CS-1 (Capability Set 1), and correspondingly, Q-1220 to Q-1229 define a set of features CS-2. The invention and its background will be described by the terminology of recommendation ETS 300 374-1 CoreINAP, but the invention can also be used in intelligent networks implemented according to other intelligent network standards.
A basic call state model (BCSM), defined in connection with the intelligent network, describes different stages of call control and includes the points at which call control can be interrupted in order to start an intelligent network service. It identifies the detection points in the call and connection process at which service logic entities of the intelligent network can have an interactive relationship with basic call and connection management features.
Referring to FIG. 1, one or more service control functions (SCF) are associated with intelligent network architecture. The equipment or network element carrying out the tasks determined for the SCF is called a service control point (SCP). Within the scope of the present application, SCF and SCP are equal, and will hereinafter be called SCP. The SCP gives call set-up instructions to the exchange, or the exchange may inquire call set-up instructions from the SCP. If the interface of subscriber B is found to be busy at some stage, of call set-up, for example the call can be directed to an alternative number. FIG. 1 also shows other elements of an intelligent network which are relevant to the understanding of the invention, such as a call control function (CCF) comprising high-level call handling functions of an exchange EXC1, EXC2, such as establishing and releasing transfer connections. Service data function SDF and service data point SDP form a database comprising subscriber-specific and/or service-specific information. Specialized resource function SRF is an interface for network mechanisms associated with interaction with a subscriber. It can be associated with what are known as intelligent peripherals (IP) and comprise, for example, more advanced speech handling functions than do exchanges in general.
Service switching function (SSF) is an interface between the call control function CCF and the service control function SCP. The network element carrying out the SSF is called a service-switching point (SSP). An intelligent network service is produced by the service switching point SSP inquiring instructions from the service control point SCP by means of messages to be transmitted across the SSP/SCP interface upon the encounter of detection points associated with the services. In intelligent network terminology these messages are called operations. In connection with an intelligent network service, a service program is started at the service control point SCP, the operation of the program determining the operations transmitted by the SCP to the SSP at each stage of a call.
FIG. 2 shows the operation of a prior art intelligent network at detection points. In step 2-1 the SSP transmits to the SCP an InitialDP operation containing the necessary data for setting up a call. Next, the detection points are armed at the SSP. In step 2-2 the SCP transmits to the SSP a message RequestReportBCSMEvent, notifying the SSP which encounters of the detection points it is to report to the SCP. Next, in step 2-3, the SCP typically transmits charging and/or interaction operations, such as FurnishChargingInformation (store charging information associated with the intelligent network service) or PlayAnnouncement (supply subscriber with an announcement associated with the intelligent network). In step 2-4 the SCP transmits to the SSP a routing instruction, such as CollectInformation (collecting dialling information from the subscriber), Connect (route call to a new number), Continue (continue call set-up with the same data) or ReleaseCall (release the connection). In intelligent network recommendations, call set-up is divided into given rough phases called Point-In-Calls (PICs). It is possible that the SSP has been configured to continue call set-up from phase PIC 2 in response to a CollectInformation operation and to continue call set-up from PIC 3 in response to a Connect operation, and so on.
There are two kinds of detection points. The above events in FIG. 2 relate to a detection point called a trigger detection point (TDP). The SSP may make an initial inquiry to the SCP in connection with such a TDP detection point, and receives instructions for call set-up. Another type of detection point is what is known as an event detection point (EDP). 2-5 in FIG. 2 shows the moment when such an EDP detection point is encountered during call set-up. The SSP reports the encounter of the detection point DP# to the SCP which transmits more call set-up instructions to the SSP in step 2-7.
The above intelligent network architecture can also be applied to a mobile communication system, in which case exchanges EXC would be replaced by a mobile services switching centre MSC. It should be noted that the SCP can be implemented as an internal process within an exchange, and charging control between the SCP and the SSP (i.e. the SCF and the SSF) then takes place within the exchange. The interface is not necessarily a CoreINAP interface, but it can be any interface having the corresponding features.
It is a problem in known intelligent network architectures, particularly in connection with mobile communication systems, that they do not define a mechanism by means of which the service control point SCP could be notified of the use of supplementary services or of the activoatin of the supplementary services at the service switching point SSP. This is especially a problem when supplementary services or supplementary operations are recurrently reported during a call. One recurrently reported matter is the change in the number of in-call channels in high-speed data transmission in which several channels are assigned to a single call. Another similar situation is Quality of Service (QoS) of an ATM connection, comprising such parameters as transmission rate, maximum delay and probability of packet loss. A third example of supplementary services which are recurrently reported is the use of what is called a prepaid SIM card (prepaid SIM service). The purpose of this service is to provide a mobile communication system of the GSM type with prepaid SIM cards (Subscriber Identity Module). The use of these cards is similar to that of a prepaid phonecard, i.e. the user of a mobile station can purchase a smart card similar to the SIM card, in which a call time is preprogrammed for a given sum of money. Although for the subscriber the use of the prepaid SIM card is similar to that of the prepaid phone card, its operation is totally different for a network and for a telephone operator, since equipment which reduce call time programmed in the card cannot be installed in the mobile station (at least afterwards). In case it is a desire to implement such a prepaid SIM service, it is to be done on the network side. The above intelligent network standards are not provided with a mechanism to inform the service control point SCP of such services.
Detection points defined in network architectures are a primary mechanism to report different events. There are two different kinds of detection points. Event detection point response required (EDPR) is a detection point upon the encounter of which the handling of the call stops at the switching point until the service control point SCP sends further instructions. Event detection point notification (EDPN) is a detection point upon the encounter of which the SSP simply transmits a message to the SCP and continues without further instructions from the SCP. The EDPR detection points have a quality of forming a what is called a control relationship. Only one control relationship can be associated with a call in accordance with intelligent network standards. A problem associated with the EDPR detection points is therefore that they prevent more supplementary services from being produced. On the other hand, a problem associated with the EDPN detection points is that after a detection point is encountered and reported, it is no longer armed. Consequently, they are not suitable for reporting recurrent events.
An object of the invention is to provide a mechanism suitable for reporting recurrent events in intelligent networks. In this context, an event mainly refers to the initial states of and the changes in factors which affect call charging. These data can also be called call attributes. The objects of the invention are achieved by a method which is characterized by what is disclosed in the independent claims. The preferred embodiments of the invention are disclosed in the dependent claims.
Firstly, the invention is based on the surprising finding that messages defined in prior art intelligent network architectures and associated with different detection points are not suitable for reporting recurrent events. Such recurrent events occur particularly in mobile communication systems in which a mobile station may enter a shadow region or change its location area while moving, whereupon the criteria of charging the mobile station may change, for some reason or other. The normal mechanism to report detection points is that the detection points which are to be reported to the SCP by the SSP are transmitted as parameters to a message RequestReportBCSMEvent by the SCP. Correspondingly, the SSP reports the encounter of these detection points in a message EventReportBCSM. In principle, these messages could be implemented differently so as to solve the above problems. However, this would require a significant change in standardization. Another option would be simply to re-arm the detection points after each report. However, this would result in a significant message traffic between the service switching point SSP and the service control point SCP. A better result is obtained if given messages defined in intelligent network standards are used in a new manner and sense. Messages particularly suitable for use include RequestNotificationCharging and EventNotificationCharging according to CoreINAP recommendations, the detailed contents of the messages being undefined. It is an advantage of the method of the invention that it is also suitable for reporting recurrent current events. Before starting charging, the service control point SCP may request the service switching point SSP to report on the events which affect call charging, whereby the SCP is capable of influencing the call charging in a variety of ways.
The method according to a first preferred embodiment of the invention for reporting events which affect a call tariff is therefore characterized in that:
call tariff formation is based on at least one attribute representing call state and/or at least one call-related resource, service and/or supplementary service;
the service control point forms the call tariff at the very beginning of tariff monitoring on the basis of an initial value of said at least said one attribute of which it has been notified by the service switching point;
during a call, the service switching point reports to the service control point at least those call-related events in which said at least one attribute may change;
in response to the report from the service switching point, the service control point re-forms the existing call tariff.
The service switching point is preferably configured to report at least given types of events without a separate request from the control point. In addition, the service control point may preferably improve a configuration which includes a default value by notifying the service switching point of events which are to be reported by the service switching point.
A preferably reported matter deals with resources assigned to the call and/or resource changes, the resources comprising transmission connection quality and/or data rate, such as the number of channels in high-speed data transmission. To reduce the number of separate messages the switching point may notify the service control point of the initial state of the resources as early as in an intelligent network service activation command. In addition, the switching point preferably reports the events in report messages, each report comprising the corresponding event and/or the points of time at which the resource change takes place. Hence, the control point SCP will be notified of the exact time of the event, even if the report is for some reason delayed. Such events may include supplementary service activation, call release, call re-establishment, data rate change, entry into and return from a shadow region by a mobile station, and a tariff change based on time.
Furthermore, a connection without control relationship is preferably established between the service switching point and the service control point, and the events on said connection without control relationship are preferably reported by the switching point. In this way, other supplementary services are not hampered or prevented from being activated.
The invention does not require any changes in equipment. It only requires slight changes in software of the service control point and the service switching point and/or in the intelligent network standard, as the invention can be implemented by the use of the existing messages in a new manner for a new purpose. For example, the invention is suitable for use in supporting the following types of services in the intelligent network:
formation of a charging record at the SCP on the basis of information reported by the SSP (this feature enables different types of in-call events to flexibly influence the contents of the charging record);
tariff transmission from the SCP to the SSP as a response to the event data obtained;
forwarding of the charging record or charging data to a person having rented a telephone without a need to post-process the charging records, which would normally take place in a billing centre;
restriction on an in-call tariff;
use of the above-mentioned prepaid SIM card.
In accordance with a preferred embodiment, no control relationship is used between the service control point SCP and the service switching point SSP during reporting, the connection of the invention between the SCP and the SSP then making it possible to affect the charging records (by SendChargingInformation and FurnishChargingInformation operations, for instance). Consequently, other services requiring an in-call control relationship are not prevented from being started (such services include hold, enquiry call, call transfer, and so on). In-call events which are caused and/or reserved by an intelligent network service which requires a control relationship are reported to the charging connection in all cases irrespective of other possible services and the fact that the intelligent network service has reserved data on the events.
It is a significant advantage that the request by the SCP to report the events which affect charging is to be sent only once. In other words, there is no need to repeat the request each time an event which affects charging is carried out. The exchange notifies the SCP of the tariff data at the beginning of the call. It can request the SSP to report the following types of events which affect charging:
answer and call release;
entry into and return from a shadow region by a mobile station subscriber (in which case time charging is stopped and re-started, respectively, in accordance with the GSM recommendations, for example);
information on handover (in which case a frequency range and/or the number of channels used in high-speed data transmission may change);
in-call supplementary service (such as hold, enquiry call, call transfer, and so on), possibly via another SCP connection;
call tariff change.
In addition, each event preferably includes a corresponding time stamp. In accordance with a simple alternative, the SCP forms a time stamp on the basis of its own clock. However, time charging is more accurate if the MSC/SSP attaches a corresponding time stamp to each report. Consequently, the report messages become somewhat longer. However, time charging is accurate even if the MSC/SSP would not manage to transmit the report message immediately after the detection of the event to be reported. It is capable of reporting even several events in the same report message.
The SCP forms a charging record on the basis of the event reports, and their time stamps obtained by the SCP. In other words, the relevant time of the events is indicated by the time according to the time stamp rather than by the point of time at which the SCP received information on the event in question.
The report given by the SSP does not require an immediate reply from the SCP. The connection according to the invention allows the SSP to inquire the charging record of the call from the SCP upon the termination of the call, after the connections to the incoming and outgoing sides have been released by the exchange.
A service started next in turn can be notified of the existence of the SCP/SSP connection of the invention. A feature interaction manager (FIM, not separately shown) can then prevent another service which affects charging from being started, in case the services are incompatible, for example.
Call state models of the SSP call control function maintain information on the attributes which affect call charging. These attributes represent call features and resources assigned to the call. These attributes may include call-related supplementary services, the number of channels and the quality of a wired and/or wireless transmission path, and so on. Upon starting a call or a supplementary service, the SSP reports a list of enumerated attributes and their values to the SCP. The list is not necessarily a fixed one but it may vary according to the service to be started. The attributes to be reported to the SCP are defined in connection with intelligent network triggering. Using these attributes the SCP defines the call tariff in more detail. Besides the attributes, the SSP notifies the SCP of the basic tariff the SSP has obtained by a number analysis. A more accurate tariff is derived from the basic tariff by examining the attribute values. Correspondingly, the SCP gives the SSP a list of those attributes whose value changes are to be reported to the SCP. When a value of an attribute belonging to the latter list changes, the changed attribute and its value are reported to the SCP together with the time stamp of the moment of change. On the basis of this information, the SCP forms an altered tariff which is considered to be valid from the point of time indicated by the time stamp. Upon termination of the call the SCP forms an accurate charging record which is based on the period of validity of different attributes and information on complete charging interruptions (because the call is temporarily dropped, for example). The charging record is transferred for post-processing through the SSP, for example. The needs and restrictions set by the post-processing define the detailed structure of the charging record.